The present invention relates generally to panel fasteners, and particularly to panel fasteners for large insulated panels like those used to form cooler room walls, floors and ceilings.
Commercial walk-in coolers, like those commonly found in convenience stores and commercial food storage facilities such as super markets, are typically constructed of insulating wall, ceiling and floor panels that are fastened snugly together. The panel ends are shaped to fit together in tongue and groove fashion and are provided with latch type fasteners for drawing and holding adjacent panels together. The latches themselves commonly comprise a hook and cam assembly that is mounted to one panel for latching engagement with a pin that is mounted to an adjacent panel.
There are two main types of panel fasteners, nail-in-place and winged. Both types have a casing with two side walls formed with an annular opening defined by a boss with a curved lip. A cam has a shaft journaled in the boss and a hook mounted in camming engagement with it. Examples of these fasteners are shown in U.S. Pat. Nos. 3,784,240 and 3,671,006, respectively.
A casing boss with a curved lip is substantially easier and more economical to produce than one with a straight lip. However a curved lip renders the casing more susceptible to spreading in the area about the boss. As the hook engages the pin and pulls it, the cam shaft exerts a force on the side of the boss nearer to the pin. As a result, curved lipped boss exerts a spreading force on the casing.
This tendency for the casing to spread or bulge is even greater when the latch and pin are misaligned. Winged fasteners are usually mounted by being foamed in place using methods similar to the one shown in U.S. Pat. No. 5,212,924. Foam is injected inside the panel. As it hardens the fasteners become secured in place. Foam hardening often causes the casing of the hook to cock out of mutual alignment. As a result, when the hook engages the pin and pulls on it, the cam shaft pushes against the front of a casing side wall and spreads the hook assembly casing walls apart. The force exerted by the hook on the casing side wall, in combination with the funneling action of the boss, can even cause one side of the cam shaft to pull out of the boss opening and the fastener to malfunction.
The nail-in fastener hook assembly casings also often spread or bulge even though they are mounted to boards usually made of hardened foam. Foam boards are used because they provide good insulation, are inexpensive to manufacture, and are resistant to rotting and water damage. Upon fastening a nail-in panel fastener hook with a pin, the force on the hook often causes the foam board to be crushed or crinkled. This is attributable to the foam board lacking strength sufficient to resist spreading of the metallic walls of the casing. This crushing or crinkling of the foam board often enables the back of the casing to move closer together and the front portion to spread apart. The giving way of the foam board, in combination with the force of the cam shaft against the boss, can easily result in the casing walls spreading significantly. Indeed, the cam shaft may actually become dislodged from the boss resulting in the fastener malfunctioning.
Heretofore the two side walls of panel fastener casings have typically been held together by pins and interlocked tabs. For example, the model 1156 panel fastener that has long been sold by Kason Industries, Inc. has a two-piece casing. Each piece has a side wall with a central boss from which a mounting flange extends right angularly. Each end of each casing wall has one centrally located tab and two tabs that straddle the central tab. During assembly the two pieces are juxtaposed about so as to capture the hook and cam assembly. The tabs are then crimped or folded over each other. A dimple in the abutting tabs is then staked to the underlying tabs in securing together one end of the casing. The other open end, from which the hook emerges, is fastened together with a pin.
As previously explained, overload places a separation force on these two walls. This force can even cause the dimples to pop apart and the fastener to fail. Moreover, it is difficult to monitor the integrity of the dimples in quality control checks during manufacture. The overlapping tabs also is costly in material.
Accordingly, it is seen that a need has long existed for a panel fastener that is more resistive to bulging and failure of its casing during the high loads sometimes imparted during panel fastening. It is to the provision of a method of producing such that the present invention is primarily directed.
A method of forming and assembling a panel fastener comprises the steps of forming a casing blank with two coplanar sides unitarily connected together at one end by a bridge, bending the bridge to bring the two sides to a position parallel with each other about a portion of a hook.